The present invention relates to steerable or adaptive lighting assemblies and more specifically to solid state adaptive assemblies for directing light to different locations without physically moving lighting components.
Conventional headlights on a vehicle generate a light pattern that is directed forward to light the space in front of the vehicle during forward motion and work well when a vehicle is traveling along a straight line in the forward direction. The lighting profile in these cases often has a relatively bright light spot in the center of a wider light pattern to illuminate a long distance directly in front of the vehicle where a driver's line of sight is most often directed. When a vehicle is turning, a driver's line of sight is typically along the direction of the turn and therefore not aligned with the bright light spot in the center of the wider light pattern. Thus, while the bright spot is useful when the vehicle is travelling directly forward, the bright spot does not enhance a driver's ability to perceive danger when executing a turn.
Some headlights have been developed that include steerable lighting modules where a bright spot can be swiveled left or right to align with the direction of vehicle travel when a vehicle is travelling directly forward or when the vehicle is turning. For instance, some lights have been developed that include light modules that are mounted for rotation about a vertical axis through a range that enables the modules to direct light patterns generally along directions selected by a vehicle steering system. Thus, when a steering system turns to the left, the light modules are rotated to the left to a similar degree and when the steering system turns to the right, the light modules are rotated to the right to a similar degree.
Lights having mechanically rotating modules have two shortcomings. First, these systems require several moving parts and therefore are relatively expensive to implement. Second, because these systems include moving mechanical parts, they often require more maintenance than a conventional headlight and therefore are more expensive to maintain.
Some solid state steerable headlights have been developed that address the problems related to mechanically rotating modules. For instance, it is known to provide a one or two dimensional array of LEDs where the LEDs generate separate adjacent light fields and where different subsets of the LEDs may be illuminated to generate light patterns at different locations in front of a vehicle. For instance, in a simple example including fifteen LEDs in a row from left to right, where the first three LEDs to the left are on and the others are off, the light pattern would appear generally to the left, where the last three LEDs to the right are on and the others are off, the light pattern would appear generally to the right, and other pattern locations between the far left and far right locations would result from turning on other subsets of LEDs with the balance of the LEDs off.
While solid state steerable lights may be less costly to manufacture and have fewer maintenance problems than lights including mechanically rotatable modules, solid state lights also have several shortcomings. First, as well known in the LED lighting arts, even when LEDs are mounted closely to each other, there are dark spots between adjacent LEDs that result in dark spots or lines between the illumination fields generated by adjacent LEDs where the illumination level is noticeably lower than within the illumination fields. Dark lines in an illumination pattern are annoying to drivers, especially during turns where the dark lines are moving with respect to a scene being viewed by the driver during execution of a turn.
Second, as LEDs in an array are turned on and off to simulate mechanical rotation of a light module during a turn, the turning on and off action of the LEDs is relatively abrupt so that a driver perceives the different LED illumination fields being turned on and off in a stepwise fashion. Here, while the illumination pattern is clearly moving, the movement is stepped as opposed to being smooth and is often annoying to a driver.